Trusset Protocol - Infrastructure for Asset Tokenization

The Stock Orderbook suite consists of a single deployable contract (StockCustody) with external dependencies on StockToken, USDC, a LiquidationRouter, and optionally a lending market. This page covers the contract’s architecture, state layout, and complete function reference.

Architecture

StockCustody maintains an internal ledger of user balances using a keccak256(user, token) key scheme. Deposits move tokens from the user into the contract and credit the internal balance. Withdrawals debit the internal balance and transfer tokens out. Trade settlements move balances between users internally without any on-chain token transfer. For compliance-checked tokens (security tokens), the contract calls ISecurityToken.canTransfer on deposit and withdrawal. Internal transfers during trade settlement skip this check entirely - compliance validation is the matching engine’s responsibility.

                      +------------------+
                      |   StockCustody   |
                      |  (this contract) |
                      +--------+---------+
                               |
          +--------------------+--------------------+
          |                    |                    |
+---------v--------+  +-------v--------+  +--------v---------+
|   StockToken     |  |     USDC       |  | LiquidationRouter|
| (ISecurityToken) |  |    (IERC20)    |  |   (external)     |
+--------+---------+  +----------------+  +--------+---------+
         |                                         |
+--------v---------+                     +---------v---------+
| IdentityRegistry |                     |   LendingMarket   |
|   (indirect)     |                     | (ILendingMarket)  |
+------------------+                     +-------------------+

The IdentityRegistry is never called directly by StockCustody. It is referenced indirectly through StockToken’s canTransfer validation during deposit and withdrawal of compliance-checked tokens.

StockCustody

UUPS-upgradeable custody contract with internal ledger, trade settlement, liquidation handling, and emergency controls.

Initialization

function initialize(
    address _admin,              // Contract administrator (cannot be zero)
    address _operator,           // Settlement operator (zero defaults to admin)
    address _liquidationRouter,  // Liquidation router address (cannot be zero)
    address _usdc                // USDC token address (cannot be zero)
) external initializer

The initializer sets up the admin, operator, liquidation router, and USDC address. If _operator is address(0), it defaults to the admin address.

State Variables

Variable	Type	Description
`admin`	`address`	Contract administrator
`pendingAdmin`	`address`	Pending admin during two-step transfer
`settlementOperator`	`address`	Operator authorized for settlements
`liquidationRouter`	`address`	External router for liquidation flows
`usdc`	`address`	USDC settlement token address
`withdrawalsPaused`	`bool`	Global withdrawal pause flag
`pendingLiquidationCount`	`uint256`	Count of unsettled liquidations
`_balances`	`mapping(bytes32 => uint256)`	Total balance per user-token pair
`_lockedBalances`	`mapping(bytes32 => uint256)`	Locked balance per user-token pair
`_processedSettlements`	`mapping(bytes32 => bool)`	Deduplication for settlement IDs
`_supportedTokens`	`mapping(address => bool)`	Registered token whitelist
`_complianceChecked`	`mapping(address => bool)`	Tokens requiring `canTransfer` validation
`_frozenUsers`	`mapping(address => bool)`	Per-user withdrawal freeze
`liquidations`	`mapping(uint256 => LiquidationInfo)`	Liquidation records

Access Control

Show Modifier definitions

Modifier	Allows
`onlyAdmin`	`admin` only
`onlyOperator`	`settlementOperator` or `admin`
`onlyLiquidationRouter`	`liquidationRouter` only
`tokenSupported(token)`	Reverts if token is not registered

Admin Management

Admin transfer is a two-step process to prevent accidental transfer to an incorrect address.

function transferAdmin(address newAdmin) external onlyAdmin
function acceptAdmin() external  // only callable by pendingAdmin

function updateOperator(address newOperator) external onlyAdmin

Token Configuration

function addSupportedToken(address token, bool complianceChecked) external onlyAdmin
function removeSupportedToken(address token) external onlyAdmin

The complianceChecked flag determines whether the token requires ISecurityToken.canTransfer validation on deposit and withdrawal. Set to true for security tokens, false for USDC and other standard ERC-20s. Removing a token from the supported list does not lock user funds. Users can still withdraw unsupported tokens. New deposits and trade settlements for the removed token are blocked.

Deposit and Withdrawal

function deposit(address token, uint256 amount) external nonReentrant tokenSupported(token)

Transfers tokens from the caller into custody. For compliance-checked tokens, validates canTransfer(caller, custody, amount) before transfer. The caller must have approved the custody contract for the deposit amount.

function withdraw(address token, uint256 amount) external nonReentrant

Withdraws available (unlocked) tokens from custody. Blocked if the user is frozen or withdrawals are globally paused. For compliance-checked tokens, validates canTransfer(custody, caller, amount). Allows withdrawal of unsupported tokens to prevent fund lockout after token removal.

function checkTransferability(
    address token, address from, address to, uint256 amount
) public view returns (bool canDo, uint8 code, string memory reason)

Pre-checks whether a compliance-checked token transfer would succeed. Returns success for non-compliance-checked tokens. Use this off-chain before deposit or withdrawal to avoid wasted gas.

Balance Locking

The operator locks user balances when orders are matched, before settlement.

function lockBalance(address user, address token, uint256 amount, bytes32 lockId)
    external onlyOperator tokenSupported(token)

Locks amount from the user’s available balance (total minus already locked). Reverts with InsufficientBalance if available balance is insufficient.

function unlockBalance(address user, address token, uint256 amount, bytes32 lockId)
    external onlyOperator tokenSupported(token)

Unlocks previously locked tokens. Reverts with InsufficientLockedBalance if the locked balance is less than amount.

Trade Settlement

function settleTrade(
    bytes32 settlementId,
    address maker, address taker,
    address baseToken, address quoteToken,
    uint256 baseAmount, uint256 quoteAmount,
    bool makerIsBuyer
) external onlyOperator nonReentrant

Atomically transfers locked base tokens from seller to buyer and locked quote tokens from buyer to seller. Both parties must have sufficient locked balances. The settlementId must be unique - reuse reverts with SettlementAlreadyProcessed.

function batchSettleTrades(
    bytes32 batchId,
    bytes32[] calldata settlementIds,
    address[] calldata makers,
    address[] calldata takers,
    address[] calldata baseTokens,
    address[] calldata quoteTokens,
    uint256[] calldata baseAmounts,
    uint256[] calldata quoteAmounts,
    bool[] calldata makerIsBuyers
) external onlyOperator nonReentrant

Settles multiple trades in one transaction. Skips already-processed settlement IDs. Includes a gas guard that stops processing if remaining gas drops below 80,000 per iteration. Emits BatchSettled(batchId, settledCount, totalSubmitted) so callers can detect partial completion.

The batchSettleTrades function takes 9 calldata array parameters, which exceeds the legacy compilation pipeline’s stack limit. The Solidity compiler must use viaIR: true. See Integration for compiler configuration.

function settlePriorityTrade(
    bytes32 settlementId,
    address liquidatedUser, address buyer,
    address baseToken, address quoteToken,
    uint256 baseAmount, uint256 quoteAmount
) external onlyOperator nonReentrant

Priority settlement for liquidated positions. The liquidated user’s tokens must be locked first. Use freezeUser() before locking to prevent withdrawal front-running between the lock and settlement steps. Emits both PrioritySettlement and TradeSettled.

Liquidation

Receiving Collateral

function receiveLiquidatedCollateral(
    address token, uint256 amount, uint256 debtOwed,
    address borrower, address lendingMarket, uint256 liquidationId
) external onlyLiquidationRouter nonReentrant

Called by the liquidation router to deliver seized collateral into custody. Tokens are pulled from the router (which must have approved the custody contract) and credited to an internal liquidation pool keyed to address(this).

External Sale Settlement

function settleLiquidation(
    uint256 liquidationId, uint256 usdcReceived, address tokenRecipient
) external onlyOperator nonReentrant

Settles after the operator sells tokens through an external venue. Stock tokens transfer to tokenRecipient. USDC is pulled from the operator and sent to the liquidation router. The lending market receives a receiveLiquidationProceeds callback. If the callback reverts, settlement still completes - off-chain systems must reconcile via events.

Internal Buyer Settlement

function settleLiquidationWithBuyer(
    uint256 liquidationId, address buyer,
    uint256 tokenAmount, uint256 usdcAmount
) external onlyOperator nonReentrant

Matches liquidation tokens with a buyer who has USDC in custody. Tokens move from the liquidation pool to the buyer’s custody balance. USDC is deducted from the buyer’s internal balance and transferred on-chain to the router. Supports partial fills - the liquidation remains open until the full amount is matched. The lending market is notified via callback.

Emergency Controls

function freezeUser(address user) external onlyOperator
function unfreezeUser(address user) external onlyOperator

Per-user withdrawal freeze. Used to prevent front-running during liquidation or for compliance holds. Does not affect the user’s ability to have their balances settled by the operator.

function pauseWithdrawals() external onlyAdmin
function unpauseWithdrawals() external onlyAdmin

Global withdrawal circuit breaker. Blocks all withdrawals for all users.

Stock Split Reconciliation

function reconcileAfterSplit(
    address token, address[] calldata users,
    uint256 numerator, uint256 denominator
) external onlyAdmin

Adjusts internal balances after a stock token split. Both total balances and locked balances are multiplied by numerator / denominator using floor division. The liquidation pool balance for the token is also adjusted. Dust from rounding stays unallocated in the contract’s ERC-20 balance. Only forward splits are accepted (numerator must exceed denominator).

View Functions

Function	Returns
`getBalance(user, token)`	Total balance (locked + available)
`getLockedBalance(user, token)`	Locked balance
`getAvailableBalance(user, token)`	Available balance (total minus locked)
`isSettlementProcessed(settlementId)`	Whether a settlement ID has been used
`isTokenSupported(token)`	Whether a token is registered
`isComplianceChecked(token)`	Whether a token requires compliance validation
`isUserFrozen(user)`	Whether a user’s withdrawals are frozen
`getLiquidation(liquidationId)`	Full liquidation record (token, amount, debtOwed, borrower, lendingMarket, timestamp, settled)

Events

Event	Parameters	When Emitted
`Deposited`	user, token, amount, newBalance	User deposits tokens
`Withdrawn`	user, token, amount	User withdraws tokens
`BalanceLocked`	user, token, amount, lockId	Operator locks balance
`BalanceUnlocked`	user, token, amount, lockId	Operator unlocks balance
`TradeSettled`	settlementId, maker, taker, baseToken, quoteToken, baseAmount, quoteAmount	Trade settlement completes
`BatchSettled`	batchId, settledCount, totalSubmitted	Batch settlement completes
`PrioritySettlement`	settlementId, liquidatedUser, token	Priority liquidation trade settled
`LiquidationReceived`	liquidationId, token, amount, debtOwed, borrower, lendingMarket	Collateral received from router
`LiquidationSettled`	liquidationId, usdcReceived, tokenRecipient	External liquidation sale settled
`LiquidationSoldToBuyer`	liquidationId, buyer, tokenAmount, usdcAmount, fullyFilled	Internal buyer fills liquidation
`OperatorUpdated`	oldOperator, newOperator	Operator address changed
`TokenSupported`	token, supported, complianceChecked	Token added or removed
`LiquidationRouterUpdated`	oldRouter, newRouter	Router address changed
`UsdcAddressUpdated`	oldUsdc, newUsdc	USDC address changed
`AdminTransferInitiated`	currentAdmin, pendingAdmin	Admin transfer started
`AdminTransferCompleted`	oldAdmin, newAdmin	Admin transfer accepted
`UserFrozen`	user, operator	User withdrawals frozen
`UserUnfrozen`	user, operator	User withdrawals unfrozen
`WithdrawalsPaused`	operator	Global withdrawal pause
`WithdrawalsUnpaused`	operator	Global withdrawal unpause
`BalanceReconciled`	user, token, oldBalance, newBalance	Balance adjusted after stock split

Errors

Error	Trigger
`Unauthorized`	Caller lacks required role
`InsufficientBalance`	Available balance less than requested amount
`InsufficientLockedBalance`	Locked balance less than transfer/unlock amount
`ZeroAmount`	Amount parameter is 0
`ZeroAddress`	Address parameter is `address(0)`
`SettlementAlreadyProcessed`	Settlement ID reused
`InvalidSettlement`	Batch array lengths mismatch or empty
`TransferFailed`	ERC-20 transfer returned false
`TokenNotSupported`	Token not registered via `addSupportedToken`
`TransferRestricted(code, reason)`	Security token `canTransfer` rejected
`LiquidationNotFound`	Liquidation ID does not exist
`LiquidationAlreadySettled`	Liquidation already fully settled
`LiquidationAmountExceeded`	Requested token amount exceeds remaining liquidation amount
`BuyerInsufficientUsdc`	Buyer’s USDC custody balance too low
`UserIsFrozen`	Frozen user attempts withdrawal
`WithdrawalsArePaused`	Withdrawal attempted during global pause
`InvalidBatchSize`	Batch settlement called with empty array
`AdminTransferNotPending`	`acceptAdmin` called by non-pending address

ILendingMarket

Callback interface that lending market contracts must implement to receive liquidation settlement notifications.

interface ILendingMarket {
    function receiveLiquidationProceeds(uint256 liquidationId, uint256 amount) external;
}

Called by StockCustody when a liquidation is settled (both settleLiquidation and settleLiquidationWithBuyer). If the callback reverts, settlement still completes. Off-chain systems must reconcile via LiquidationSettled or LiquidationSoldToBuyer events.

Overview

Commodity Token License

Stock Token License

Stock Orderbook License

Commodity Orderbook License

Contracts

Architecture

StockCustody

Initialization

State Variables

Access Control

Admin Management

Token Configuration

Deposit and Withdrawal

Balance Locking

Trade Settlement

Liquidation

Receiving Collateral

External Sale Settlement

Internal Buyer Settlement

Emergency Controls

Stock Split Reconciliation

View Functions

Events

Errors

ILendingMarket

Overview

Commodity Token License

Stock Token License

Stock Orderbook License

Commodity Orderbook License

​Architecture

​StockCustody

​Initialization

​State Variables

​Access Control

​Admin Management

​Token Configuration

​Deposit and Withdrawal

​Balance Locking

​Trade Settlement

​Liquidation

​Receiving Collateral

​External Sale Settlement

​Internal Buyer Settlement

​Emergency Controls

​Stock Split Reconciliation

​View Functions

​Events

​Errors

​ILendingMarket

Architecture

StockCustody

Initialization

State Variables

Access Control

Admin Management

Token Configuration

Deposit and Withdrawal

Balance Locking

Trade Settlement

Liquidation

Receiving Collateral

External Sale Settlement

Internal Buyer Settlement

Emergency Controls

Stock Split Reconciliation

View Functions

Events

Errors

ILendingMarket